Patent Application
20080179732
The present invention relates to a working method of a metal material and a semiconductor apparatus fabricated by the method. In particular, the invention relates to a diode base for automotive alternating current generators, and rectifiers, and a manufacturing method thereof.
JP-A-8-115992 discloses a technique for forming a Cu—Mo sintered rolled material into a cup-shaped body. Also, the publication describes a forming method with drawing or squeezing.
JP-A-8-112634 describes a method of forming a sheet material with semi-punching.
JP-A-8-115992 describes forming with drawing or squeezing when a Cu—Mo sintered rolled material is to be formed into a cup-shaped body. However, the publication takes no account of crack in a material.
Also, JP-A-8-112634 describes forming of a sheet material with semi-punching. However, the publication gives no consideration to incorporation of the process, in which a projection is cut to make a cup-shaped body, material yield, and dimensional accuracy after cutting.
It is an object of the invention to provide a working method of a metal material, in which an alloy including a sintered rolled material is worked with high freedom, and a semiconductor apparatus making use of the working method.
In order to solve the problems, one of the inventions has a feature in constraining a blank comprising an alloy containing copper and performing plastic working to form an outer peripheral portion so as to form an inner space therein.
Also, the invention has a feature in that the alloy has characteristics having at least a coefficient of thermal expansion α of not less than 7 [10−6/K] but not greater than 13 [10−6/K] and a coefficient of thermal conductivity λ of not less than 150 [W/(m·K)] but not greater than 300 [W/(m·K)].
Further, the alloy is a Cu—Mo alloy or a Cu—W alloy and is subjected to plastic working by cold extrusion.
Also, the invention has a feature in that worked surfaces, to which working pressures are applied, has an area of not greater than 50% of a whole surface area of the blank.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
a) to 4(c) illustrate the process of cold forging of a diode base.
a) to 9(f) are cross sectional views showing examples of a cup-shaped configuration, which can be formed from an alloy.
a) and 11(b) are views showing a surface condition in plastic working of an alloy.
Embodiments of the invention are described with reference to the accompanying drawings.
Note that the following embodiments are those concerning an automobile alternating current generator but the present invention is not limited to these embodiments. The present invention, as described above, is one which forms a shape of an object by plastic working in order to restrain crack and variation of the dimensional accuracy resulted by working to an alloy containing copper, which is subject matter of the present invention, and is applicable to an electric instruments, electric machines, electronic instruments, device and the like. In particular, the present invention is effective in forming a cup-shape.
A rotor 1 is fixed to a rotating shaft 4 to be excited by an exciting coil 4, and generates N poles and S poles with rotor pawls 2 in a circumferential direction of the rotor according to the number of poles. The exciting coil 3 is supplied with direct current through slip rings. The slip rings each comprises a brush 7 mainly made of carbon and held by a brush holder and a brush ring 22 fixed to the rotating shaft 4. In addition, a connection terminal 5 is provided between the slip rings and the exciting coil 3 to afford connection of lead wires from the slip rings and lead wires of the exciting coil 3 there, thus improving an assembling easiness. The exciting coil 3 comprises a bobbin (not shown), which possesses electric insulation and around which lead wire with an insulating coating is wound many turns. Preferably, in order that heat generated on the exciting coil 3 is easily transmitted to the rotor, the bobbin is preferably made of a material having a small heat resistance, for example, a composite material obtained by coating an insulating paint or resin on surfaces of an organic resin such as epoxy resin, in which aluminum oxide powder is dispersed and mixed to enhance a coefficient of thermal conductivity thereof, or of metal such as iron.
Centrifugal fans 11, 12 are provided on both end surfaces of the rotor 1. Openings 8a, 8b, 9a, 9b are formed in locations on a front bracket 8 and a rear bracket 9 to be communicated to suction sides and discharge sides of the fans 11, 12. The fan 11 sucks a cooling air from the opening 8a and discharges the air from the opening 8b after passing through the front bracket. Also, the fan 12 sucks a cooling air from the opening 9a and discharges the air from the opening 9b after passing through the rear bracket. On a side of the rear bracket 9, a fan guide 21 structurally separates suction and discharge sides of the fan 12 from each other, and the openings 9a, 9b are positioned on both sides of the fan guide 21. It is desired that a blast area defined by the both brackets 8, 9 and the fan guide 21 be made as large as possible not to make a blast resistance to the fan.
A stator 24 comprises stator coils 19 embedded in slots provided on a stator core 6 composed of laminated steel sheets. The number of the slots amounts to three times the number of poles since three-phase alternating current is to be generated. The stator coils 19 comprises many turns of lead wire with an insulating coating, and insulation serving also as protection of the insulation on conductors is provided by inserting an insulating sheet between the coils and the stator core 6 in the slots. It is desired that the lead wire with the insulating coating be square wire in order to increase occupancy of the conductors in the slots. However, round wire is rather easy to manufacture and wind. In either case, varnish, resin, or the like is impregnated in voids within the slots to fix the conductors together and to permit heat generated by the coils to be easily transmitted to the stator core 6. The stator core 6 is interposed between the front bracket 8 and the rear bracket 9 to be firmly fixed thereto by means of through-bolts (not shown).
The rotating shaft 4 is rotatably supported by bearings 13 at both ends thereof on the front bracket 8 and the rear bracket 9. A pulley 10 for transmitting power from an engine is provided on a front-bracket side end of the rotating shaft 4. Support legs 8c, 9d for fixing a body of the automotive alternating current generator to an engine are provided on the front bracket 8 and the rear bracket 9. A voltage regulator 18 for regulating current to the exciting coil 3 to make generated voltage constant irrespective of the rotational speed, and a rectifier 23 for converting alternating current generated by the stator coils 19 into direct current are fixed to the rear bracket 9.
The rectifier 23 comprises diodes 20, a diode minus cooling plate 14 and a diode plus cooling plate 15, to which the diodes 20 are mounted, an insulating sheet (not shown) arranged between the both cooling plates 14, 15, a mold terminal 16, and a fixing member 17 for fixing these parts to the rear bracket 9. Concretely, the rectifier 23 is fixed to the rear bracket 9 by arranging the diode minus cooling plate 14, the insulating sheet, the diode plus cooling plate 15, and the mold terminal 16 in this order in an overlapped state from an inner side of the rear bracket 9, providing through-holes extending through these elements, passing the fixing member 17 from a side of the mold terminal 16, abutting one end of the fixing member 17 against the mold terminal 16, fixing a tip end of the fixing member to the rear bracket 9, and pressing the mold terminal 16 against the rear bracket 9.
The diode minus cooling plate 14 is made of a member having favorable thermal conductive properties and a plurality of diodes 20 is mounted on a surface of the diode minus cooling plate 14 toward the rear bracket. A thermally conductive grease or the like is applied between the diode minus cooling plate and the rear bracket 9 to reduce heat resistance between the both, so that the diode minus cooling plate 14 is thermally connected to the rear bracket 9. Thereby, heat generated by the diodes 20 is transmitted to the rear bracket 9 to be radiated from the rear bracket 9.
The diode plus cooling plate 15 is made of a member having favorable thermal conductive properties. A plurality of diodes 20 is mounted on a surface of the plate 15 opposed to the rear bracket 9. An insulating sheet constituting an insulating member and the mold terminal 16 are arranged between the diode plus cooling plate 15 and the diode minus cooling plate 14, and the plate 15 is electrically insulated therefrom and thermally connected thereto.
Desirably, the insulating sheet interposed between the diode minus cooling plate 14 and the diode plus cooling plate 15 protrudes outward from the both cooling plates 14, 15 to keep an insulation distance between positive and negative poles. The insulating sheet having a large thermal conductivity is used in order to reduce heat resistance between the diode minus cooling plate 14 and the diode plus cooling plate 15. Thereby, a part of heat generated from the diodes 20 mounted on the diode plus cooling plate 15 is transmitted from the diode plus cooling plate 15 through the insulating sheet to the diode minus cooling plate 14, and further to the rear bracket 9 to be radiated from the rear bracket 9.
The mold terminal 16 serves to fix diode terminals and stator coil lead portions, and is made of a member having electrically insulating properties. The member is desirably favorable in thermal conduction. Thereby, the fixing member 17 is electrically insulated from the diode plus cooling plate 15.
The fixing member 17 is made of a member having favorable thermal conductive properties, and thermally connected at a side end thereof and mounted to the rear bracket 9.
That is, the fixing member 17 is thermally connected to the diode plus cooling plate 15 while maintained in electric insulation therefrom, and the fixing member 17 is made favorable in thermal conductive property. Besides, the fixing member is thermally connected and fixed to the rear bracket 9. Thereby, heat generated from the diodes 20 mounted on the diode plus cooling plate 15 can be transmitted to the fixing member 17. Further, heat can be transmitted to the rear bracket 9 from the fixing member 17 to be radiated from the rear bracket 9. Thereby, it is possible to cool the diodes 20 without increasing the number of parts.
The invention includes, for example, the following constitution. That is, the invention includes a semiconductor apparatus comprising a cup-shaped diode base mounted on a radiating plate, a semiconductor chip fixed to an inner bottom surface of the diode base through a junction member, and lead wires connected to the semiconductor chip and to external devices, and wherein the diode base is made of an alloy material and has a coefficient of thermal expansion α of 7 to 13 [10−6/K] and a coefficient of thermal conductivity λ of 150 [W/(m·K)].
Preferably, the semiconductor chip is joined directly to the diode base. Also, the diode base is preferably made of a Cu—Mo sintered rolled material. Further, the diode base is more preferably made of an alloy material containing about 35% of Cu and about 65% of Mo. And the semiconductor apparatus or diodes are applied to full-wave rectifiers for automotive alternating current generators.
Also, in the case where a cup-shaped body is formed by constraining a circumference of a blank of a Cu—Mo sintered rolled material and one of surfaces to be worked with the use of a die, and applying working pressures to the other of the surfaces to be worked with the use of a working punch or a counter punch, an area, to which working pressures are applied, is preferably set to at most 50% of a whole surface area of the blank. The material is caused to flow around the working punch, thus obtaining a cup-shaped product. Alternatively, by pressing the other of the surfaces to be worked with the working punch, a product such as cup-shaped element, member, parts, or the like is obtained. The cup-shaped body constitutes the diode base.
A diode base for rectifiers comprises a cup-shaped body formed by constraining a circumference of a blank of a Cu—Mo sintered rolled material and one of surfaces to be worked, applying working pressures to the other of the surfaces to be worked with the use of a working punch or a counter punch, and setting an area, to which working pressures are applied, to at most 50% of a whole surface area of the blank.
Cooling fins comprise a rolled metal material having a wave-shaped cross section and is disposed to permit transmission of heat from semiconductors. The rolled metal material is formed by constraining a circumference of a blank of a Cu—Mo sintered rolled material and one of surfaces to be worked with the use of a die, and using a working punch or a counter punch of which end surface has a wave-shaped cross section to apply working pressures to that area of the other of the surfaces to be worked, which amounts to at most 50% of a whole surface area of the blank. The cooling fins serve also as those for semiconductors.
A diode 20 according to the embodiment is described below with reference to
As shown in
Conventionally, diode bases are made of only Cu since work crack is generated in an alloy. The diode base 27 in the invention, however, is made of a Cu—Mo alloy or a Cu—W alloy so as to prevent generation of work crack. By forming the diode base 27 from the Cu—Mo alloy, a difference in coefficient of thermal expansion α between the semiconductor chip 25 and the diode base 27 can be made smaller than that in the case where the diode base is made of Cu. Conventionally, a member having a coefficient of thermal expansion between coefficients of thermal expansion of a chip and a diode base is inserted as a cushioning material between the both in order to restrict a difference in coefficient of thermal expansion. Thus, α1<α3<α2 or α2<α3<α1 is set where α1, α2 and α3, respectively, indicate coefficients of thermal expansion of the chip, the diode base and the cushioning material. According to the embodiment, however, a difference between α1 and α2 can be made smaller than that in the related art. Thereby, a chip and a diode base can be joined directly to each other by solder. Further, by joining a chip and a diode base directly to each other by solder, a heat transfer coefficient can be heightened as compared with the case where a separate member is arranged between the both. Thereby, it is possible to improve diodes in heat radiation performance. Also, by joining a chip and a diode base directly to each other by solder, man-hour for soldering can be reduced as compared with the case where a separate member is arranged between the both. Thereby, it is possible to enhance productivity.
More concretely, the diode base is desirably made of an alloy material to have a coefficient of thermal expansion α of 7 to 13 [10−6/K] and a coefficient of thermal conductivity λ of 150 to 300 [W/(m·K)]. This is because the inventors of the present application have found as results of various examinations that setting of such numerical range leads to prevention of crack due to a difference in thermal expansion between the diode base and the chip. Also, the inventors of the present application have found as results of various examinations that as far as being within the numerical range, it is possible to ensure a heat transfer coefficient required for cooling.
Here, a method of forming a diode base from a Cu—Mo alloy is described.
Such being the case, the inventors of the present application have made various examinations with respect to a method of working an alloy with a Cu—Mo alloy as the start. As a result, it has been found that crack is very simply generated in the Cu—Mo alloy when drawing or squeezing is performed. Also, it has become apparent that crack is generated on that surface, which is subjected to tension, and such tension is resulted on many surfaces in drawing or squeezing. For example, when drawing or squeezing is applied to an alloy member as shown in
The inventors of the present application have examined a method of working sintered rolled materials with the Cu—Mo alloy as the start, in which method crack is hard to generate. A working method having been found as a result is described below.
A method of manufacturing a diode base 27 made of the Cu—Mo alloy in the embodiment is described with reference to
The procedure of working is described below. First, as shown in
Here, rearward extrusion is described. First, the blank 29 is constrained by a hollow die (or a female die) 31 and a counter punch (or a female pin) 34 (the left side in
In addition, an equivalent cup-shaped member can be obtained in the embodiment shown in
Conventionally, only very simple forming such as cutting can be performed to Co—Mo alloy since it has been not possible to overcome problems of crack. In the case where a complicated configuration is to be formed, it has been possible to select only a working method, for example, cutting, involving much man-hour. Cutting is bad in yield of material and adoption thereof is problematic in terms of productive efficiency.
However, the method found by the inventors of the present application makes it possible to form the Cu—Mo alloy into a complicated configuration while ensuring the yield of material. Here, the complicated configuration means a configuration with irregularity. That is, it is possible to form, for example, radiation fins for use in cooling of semiconductors, as well as a cup-shaped configuration having a recess as in the embodiment.
An embodiment, in which radiation fins are formed, is described with reference to
The fin working punch 101 has a mountain-shaped cross section at a tip end thereof. The punch is guided by the guide 32 to press a blank 29. In this extrusion, most portions of external surfaces of the blank 29 can be constrained by the fin working punch 101, the hollow die 31, and the counter punch 34. Such constraint makes it possible to prevent crack due to tension applied on the constrained surfaces. That is, when the fin working punch 101 is pushed downward in
In the embodiment, cutting is performed to obtain the blank 29. As shown in, for example,
While drawing or squeezing mainly generates tensile stress to thereby cause crack or the like in a material, rearward extrusion forming in the embodiment mainly generates compressive stress whereby forming can be made without generation of crack or the like in a material.
In addition, in the case of plastic working, for example, rearward extrusion of an alloy according to the invention, the blank 29 is constrained by the female pin 34 and the female die 31 and worked by means of the working punch 33, the alloy flows rearwardly of the working punch 33. When a cross section of the product is cut and a structure thereof is observed, flow of metal can be seen as shown in
According to the respective embodiments described above, it is possible to provide a semiconductor apparatus having a high cooling capacity. Also, a method of manufacturing a diode base is provided to be high in accuracy and excellent in productivity.
Also, since the Cu—Mo alloy can be worked in plastic working, it is possible to attain an improvement in yield of material as compared with the case in cutting.
Also, it is possible to provide a semiconductor apparatus enhanced in cooling capacity.
The invention can be applied to members, parts, elements, or products, which are to be formed in plastic working from alloys including the Cu—Mo alloy, realize members, parts, elements, or products, which are enhanced in cooling capacity, and bring about an excellent productivity.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-018185 | Jan 2003 | JP | national |
This application is a continuation of U.S. patent application Ser. No. 11/437,808 filed May 22, 2006 which is a continuation of U.S. patent application Ser. No. 10/753,406 filed Jan. 9, 2004, which claims priority to Japanese patent application Serial No. JP2003-018185 filed Jan. 28, 2003, the disclosures of which are incorporated herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10753406 | Jan 2004 | US |
| Child | 11928832 | US | |
| Parent | 11437808 | May 2006 | US |
| Child | 10753406 | US |
